Furnace



G. J. HAGAN.

FURNACE.

APPLICATION FILED MAY 14, 1920.

Patented Decl14,1920.

2 SHEETS-SHEET 1.

G. J. HAGAN.

FURNACE.

APPLICATION man mAy14,1-92o.

1,362,297. Patented De0.14,1920.

2 SHEETS-SHEET 2.

INVENTO R iJNlTED STAlES PATENT OFFICE.

summon.

Specification of Letters Patent.

Patented Dec. let, 1920.

Application filed May 14, 1920. Serial No. 381,297.

To all whom it may concern:

Be it known that I, GEORGE J. HAGAN, residing at Pittsburgh, in the county of Allegheny and State of Pennsylvania, a citizen of the United States, have invented or discovered certain new and useful Improvements in Furnaces, of which improvements the following is a specification.

It has been found difficult in furnaces, when the char 'e to be heated extends to within a short distance of the walls to properly heat the lower portions of the charge or those portions in proximity to the bottom ofthe heating chamber. This difiiculty is experienced particularly in box annealing furnaces and furnaces for heating large bodies such as ingots, which will extend a considerable distance above the bottom of the heating chamber, and will so approximate the size of the heating chamber that the spaces between the walls of the chambe and the charge will be narrow, and hence as the heat and products of combustion in addition to their natural tendency to rise, must pass upwardly over the box on their way to the exit flues, the lower portions of the box or ingot being outside of the path of flow of the products of combustion, receive compa a ively little heat directly, but are heated principally by conduction from the upper portions of the box and its contents.

The invention described has for its object the provision of means whereby heat and products of combustion may be caused to flow down between the wall and box and the lower portions of the box subjected to direct action of the heat and products of combustion. The invention is hereinafter more fully described and claimed.

In the accompanying drawings forming a part of this specification Figure 1 is a sectional elevation of a furnace embodying the improvements claimed herein; and Fig. 2 is a sectional plan view of the same.

In the practice of the invention the furnace is constructed with a lire box 1 and a combustion chamber 2. In annealing and ingot heating furnaces the heating chamber is generally made of suflicient length to permit of a plurality of annealing boxes or ingots indicated at 3, being arranged in tandem and having transverse dimensions sufliciently greater than those of the boxes or ingots that there may be spaces 6 between the sides of the box or ingot and the walls of the chamber, for the circulation of heat and products of combustion. As the fine 5 for the escape of the products of combustion is generally connected to the heating chamber adjacent to the bottom of the chamher, no difliculty is experienced in heating the sides of the boxes or ingots adjacent to the sioes of the heating chamber 2 from which the flue 5 extends. But on account of the narrowness of the spaces between the other sides of the heating chamber and the sides of the boxes or ingots, the movement of heat and products of combustion is so relatively small that the heating of the lower portions of the boxes or ingots is slow and inefficient. This is especially true as regards the space between the bridge wall and the boxes or ingots for the reason that the boxes or ingots extend a considerable distance above the bridge and as the heat and products of combustion are drawn upward and across the space or pocket 6 between the bridge wall and the sides of the boxes or ingots, they'will tend to exhaust the heat and products of combustion from such space or pocket or at least prevent a sufiicient flow of heat down into such pocket as to heat the portions of the boxes or ingots below the level of the top of the bridge and adjacent thereto at the same rate or to the same degree as other portions are heated.

As the temperature of the sides of the boxes or ingots is progressively le s toward the bottom of the heating chamber, there will be a corresponding decrease in the pressure of the gases in the spaces or pmkets 6, between the walls of the chamber and the sides of the boxes or ingots and hence there will be a downward movement of gases along the sides of the boxes and an upward movement along the surfaces of the walls of the heating chamber, said walls being hotter than the boxes or ingots. While this circulation will tend to promote the heating of the inner portions of the boxes or ingots, it is slow due to the fact that the spaces in which such circulation occurs, are confined, and also to the reverse movements of the two streams which tend to retard their rate of movement.

In order to obtain a more rapid flow of gases through these spaces or pockets provision is made to partially or wholly segregate these oppositely moving streams of gases. To this end vertical passages 7 are formed in the walls of the heating chamber and connected to the heating chamber at points adjacent to the bottom of said chamber, as shown in Figs. 1 and 2. Thesepassages extend upwardly substantial distances, having their outlets so located that the gases flowing upwardly from these passages will not interfere with the movement of gases down along the sides of the boxes or ingots. These passages are preferably formed as close as practicable to the inner surfaces of the walls of the heating chambers, so that the walls of said passages will be highly heated so as to reheat the gases entering the lower ends of the passages and whereby their rate of movement is accelerated.

The open upper ends of the passages 7 are so located relative to the flow of gases through the furnace that the latter will have an aspirating effect on the gases in the passages and thereby accelerate their rate of movement.

By reference to Fig. I it will be observed that the furnace is so constructed that a vertical plane coincident with the median line of the heating chamber will be a substantial distance from a vertical plane coincident with the center of the arch forming the top of the furnace. By reason of this construction the space between the top of the annealing box, when in position in the heating chamber, and the arch is gradually reduced in height in the direction of flow of the gases through the furnace, thereby causing an increase of pressure of the gases above the a passage having its inlet communicating 'with the heatin chamber at a oint ad'acent to the bottom thereof and its outlet so located that the gases flowing from the point of combustion will flow across such outlet and cause a flow of gases from the heating chamber through such passages.

2. A furnace for heating large bodies such as ingots, annealing boxes, etc., having vertical passages formed in the side of the heating chamber, the lower ends of said passages communicating with the heating chamber at points adjacent to the bottom of the chamber and their upper ends communicating with the said chamber at points a substantial distance above their inlets.

3. A heating furnace having in combination a fire box and a heating chamber the roof of said furnace spanning said box and chamber, whereby the median line of the roof will be intermediate the bridge wall and the median line of the heating chamber, so that when an annealing box is placed in position in the heating chamber a passage for the gases will be formed intermediate the arch and the top of the box, said passage decreasing in height inthe direction of flow of the gases.

In testimony whereof, I have hereunto set my hand.

GEORGE J. HAGAN. 

